1. Field of Invention
The invention relates to a method and apparatus for regulating electrical power output of a fuel cell system.
2. Description of the Related Art
U.S. Pat. No. 5,432,710 A describes a power supply system that contains a fuel cell and a controller. The controller regulates the systems and subsystems of the power supply system by minimizing a cost function in the form of an algebraic equation. This cost function takes into account the power demand of the load, the power demand of the system itself, and the exhaust gases. In dependence on the cost function, the controller sets the mass flow of an oxidant stream and the mass flow of a hydrogen-rich gas for the fuel cell unit, and the mass flow of a fuel for the reformer.
JP 59-11270 describes a fuel cell system comprising differential pressure controlling valves for controlling a differential pressure between the pressures of supplied oxygen and hydrogen. The hydrogen is supplied from a hydrogen tank. The differential pressure control valves are connected to each other by a link mechanism. Thus, the operation of one pressure control valve is controlled in dependence on the operation of the respective other differential pressure control valve.
JP 5911273 describes a similar fuel cell system with two pressure control valves which are controlled in dependence from the respective other pressure control valve.
EP 1 207 578 A2, which is not prepublished, describes a fuel cell system wherein the hydrogen is supplied from a high pressure hydrogen tank to the fuel cell system. In this document it is mentioned that pressure hydrogen supplied from the high pressure hydrogen tank to the fuel cell is based on the air pressure supplied from the air supply side. That means that the pressure of the hydrogen supplied to the fuel cell system is controlled in dependence on the air pressure supply from the air supply side.
There is a need for improvement in regulating power supply from a fuel cell to a load. The present invention addresses this need and provides further related advantages.